I am not doing floor presses anymore either, they hurt my damn shoulder.
As for tricep movements, I use a bar movement (JM press, 5 board press, skullcrusher) on dynamic day, and a dumbell movement on max effort day, either tricep extensions or elbows out tricep extensions. On dynamic day I do pressdowns for 3 sets after all other exercises, but on max effort day I do not. Not any real great science behind this, just that with the dumbells, I feel like so much blood is going into the tri's that they are going to pop, and on dynamic day with the heavier bar movement, I don't feel much of a pump, so I hit some tricep pressdowns to get some blood in there. This has worked well for me so far, but if it stops working I will damn sure be doing something else.
As far as the tricep not knowing what exercise you are asking it to do, the central nervous system damn sure knows though, cause you will get weaker if you continually do the same move over and over.
B